The area covered by this guide falls within the Coastal Plain region of the southeastern United States, which contains some of the most unique ecosystems in North America. It’s a place where water is never far away and always features large in the daily lives, economy, and folkways of the region’s people.
The ancient geography of the region determines the nature of the coast today, still in a profound state of flux from a variety of factors. Though it’s hundreds of miles away, the Appalachian Mountain chain has a major influence on the southeastern coast. It’s in Appalachia where so much of the coast’s freshwater—in the form of rain—comes together and flows southeast—in the form of rivers—to the Atlantic Ocean.
Moving east, the next level down from the Appalachians is the Piedmont region (in South Carolina often called simply the Upstate). The Piedmont is a hilly area, the eroded remains of an ancient mountain chain now long gone.
At the Piedmont’s eastern edge is the fall line, so named because it’s there where rivers make a drop toward the sea, generally becoming navigable.
Around the fall line zone in the Upper Coastal Plain you can sometimes spot sand hills, usually only a few feet in elevation, generally thought to be the vestigial remains of primordial sand dunes and offshore sandbars. Well beyond the fall line and sometimes nearly invisible sand hills lies the Lower Coastal Plain, gradually built up over a 150 million-year span by sedimentary runoff from the Appalachian Mountains, then as high or even higher than the modern-day Himalayas.
The Coastal Plain was sea bottom for much of the earth’s history, and in some eroded areas you can see dramatic proof of this in prehistoric shells, shark’s teeth, and fossilized whale bones and oyster beds, often many miles inland.
Sea level has fluctuated wildly with climate and geological changes through the eons. At various times over the last 50 million years, the Coastal Plain has submerged, surfaced, and submerged again.
At the height of the last major Ice Age, when global sea levels were very low, the east coast of North America extended out nearly 100 miles farther than the present shoreline. (We now call this former coastal region the continental shelf.) The Coastal Plain has been in roughly its current form for about the last 15,000 years.
© Jim Morekis from Moon Charleston & Savannah, 4th Edition